1. Field of the Invention
The present invention relates to an image aspect ratio converting apparatus for converting an image material having an aspect ratio of 4:3 such as NTSC, PAL or SECAM to a wide image material having a different aspect ratio (e.g., an image material of a high vision having an aspect ratio of 16:9 and 480i). More particularly, it relates to an aspect ratio converting apparatus which performs the image processing of both ends in the horizontal direction of the wide image material obtained by the conversion.
2. Description of the Related Art
In a present broadcasting system, a screen aspect ratio is 4:3, but in a high vision, a transversely prolonged wide screen is used in which the screen aspect ratio is set to 16:9. The widening of this television screen is indispensable to regenerate an image more powerful than ever and to provide the feeling of realism. Moreover, television sets with a transversely long screen size (16:9) have actually been manufactured and spread.
In this case, a still image material having an aspect ratio of 4:3 is converted to a still image material having a wide aspect ratio (e.g., 16:9) so as to regenerate a similarly powerful image on a wide television screen.
However, when the still image material having an aspect ratio of 4:3 is outputted as it is onto the screen having an aspect ratio of 16:9, non-image portions inconveniently appear on both the ends in a horizontal direction on the screen having an aspect ratio of 16:9.
Therefore, as a countermeasure, in a conventional image aspect ratio converting apparatus, certain images colored, for example, black, green or blue are allotted to both the ends in the horizontal direction of the image having an aspect ratio of 16:9.
However, in the conventional system in which certain image signals are allotted to both the ends in the horizontal scanning direction of an image signal having the converted wide aspect ratio, the image looks as if a frame were fixed to both the ends, thereby resulting in the image lacking in natural property.
The present invention has been developed in consideration of the above-described situations, and an object thereof is to provide an image aspect ratio converting apparatus in which when an image material having an aspect ratio of 4:3 is outputted as it is to a screen having a wide aspect ratio, the image material can be converted to the image material having a wide aspect ratio while a natural property is held.
To attain the above-described object, there is provided an image aspect ratio converting apparatus comprising: aspect ratio converting means for converting an image signal having an aspect ratio of 4:3 to an image signal having a predetermined wide aspect ratio; image extracting means for extracting a predetermined amount of a left end image and a predetermined amount of a right end image of a horizontal scanning period of the image signal having an aspect ratio of 4:3; and extrapolating means for using the extracted predetermined amount of the left end image to extrapolate a region of from the left end of the horizontal scanning period of the image signal having an aspect ratio of 4:3 to the left end of the horizontal scanning period of the image signal having the wide aspect ratio, and for using the extracted predetermined amount of the right end image to extrapolate a region of from the right end of the horizontal scanning period of the image signal having an aspect ratio of 4:3 to the right end of the horizontal scanning period of the still image signal having the wide aspect ratio.
According to the present invention, on the basis of the predetermined amounts of left and right end images of the horizontal scanning period of the image signal having an aspect ratio of 4:3, the extrapolation is performed for a region of from the left end of the horizontal scanning period of the image signal having an aspect ratio of 4:3 to the left end of the horizontal scanning period of the image signal having the wide aspect ratio, and a region of from the right end of the horizontal scanning period of the image signal having an aspect ratio of 4:3 to the right end of the horizontal scanning period of the image signal having the wide aspect ratio.
Therefore, the image material having an aspect ratio of 4:3 can be converted to the image material having the wide aspect ratio while the natural property is held.
In a preferred embodiment for carrying out the present invention, the extrapolating means repeatedly applies one to several samples of images generated from the extracted predetermined amount of the left end image to the region of from the left end of the horizontal scanning period of the image signal having an aspect ratio of 4:3 to the left end of the horizontal scanning period of the image signal having the wide aspect ratio, and repeatedly applies one to several samples of images generated from the extracted predetermined amount of right end image to the region of from the right end of the horizontal scanning period of the image signal having an aspect ratio of 4:3 to the right end of the horizontal scanning period of the image signal having the wide aspect ratio.
According to this embodiment, the extrapolation of both the left and right ends can be performed by repeatedly applying the same image.
In another preferred embodiment for carrying out the present invention, the extrapolating means extrapolates the region of from the left end of the horizontal scanning period of the image signal having an aspect ratio of 4:3 to the left end of the horizontal scanning period of the image signal having the wide aspect ratio with an image so generated from the extracted predetermined amount of the left end image as to have a monotonously decreased gradation property, and extrapolates the region of from the right end of the horizontal scanning period of the image signal having an aspect ratio of 4:3 to the right end of the horizontal scanning period of the image signal having the wide aspect ratio with an image so generated from the extracted predetermined amount of the right end image as to have a monotonously decreased gradation property.
In the preferred embodiment for carrying out the present invention, the gradation property comprises at least one of luminance, hue, and xcex3 property.
According to this embodiment, the gradation property can be changed to thereby extrapolate both the left and right ends.
In another preferred embodiment for carrying out the present invention, the extrapolating means extrapolates the region of from the left end of the horizontal scanning period of the image signal having an aspect ratio of 4:3 to the left end of the horizontal scanning period of the image signal having the wide aspect ratio with an image so generated from the extracted predetermined amount of left end image as to have a gradually increased defocus amount, and extrapolates the region of from the right end of the horizontal scanning period of the image signal having an aspect ratio of 4:3 to the right end of the horizontal scanning period of the image signal having the wide aspect ratio with an image so generated from the extracted predetermined amount of right end image as to have a gradually increased defocus amount.
According to this embodiment, the defocus amount of the image can be changed to thereby extrapolate both the left and right ends.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.